The only graph that will logically map incomplete/non-regular date value is a scattergraph.
Unlike the other charts, A scattergraph will distribute values across the X axis based on the maximum and minimum values. All other charts assume each row is a distinct value set.
Here's the same data mapped to a regular column and a 2D scatter chart:

You can see that the values on the scatter chart are distributed between the min and max values, not simply adjacent to each other.
If you want the scatter chart to look more like a column chart, you can do that... select the chart, then go Inspector -> Series -> Y Axis Error Bars -> 100 Percent, then click on one of the error bars and go Inspector -> Error Bar -> and make the error bar wider and the same color as the data point:

and you should see something like this:

2D Scatter chart masquerading as a bar chart.
Or, for a line chart, turn on Connection Lines (Inspector -> Series -> Connection Lines):

2D Scatter chart masquerading as a line chart.